Integration of large-scale heat pumps to assist sustainable water desalination and district cooling

Abstract

Climate change intensifies stress on global potable water supply. Over 2 billion people still lack access to safe potable water, hindering social and economic development in arid regions. As a result, cost-effective desalination is important. The two main desalination technologies are thermal-based and membrane processes. The membrane-based desalination process Reverse Osmosis is gaining more and more popularity. The reason is that thermal-based processes often rely on non-renewable heat sources, while high temperature heat pumps offer a sustainable alternative for heat supply. Thus, this study investigates the integration of a transcritical CO2 heat pump into thermal-based desalination processes. The CO2 process operates at up to 180 °C, with an eco-friendly working fluid. The heat pump provides both potable water and potentially cooling energy. Six configurations were considered, showing comparable energy demands to RO. Moreover, considering cooling duty, the integrated system outperforms RO. A commercially available 19 MWel transcritical CO2-based heat pump system can produce up to 64.000 m3/d of potable water and 75 MW of cooling energy. This highlights the potential of heat pumps as sustainable solutions for addressing water scarcity and providing cooling.